1. Field of the Invention
The present invention relates to an upgraded bead breaking unit for tyre changing machines or the like.
2. Description of the Related Art
Tyre changing machines are commonly used for fitting/removing vehicle wheel tyres to/from respective rims
As is known, before being able to completely remove a tyre from its housing on the respective rim, it is necessary to detach the beads thereof from the bead retention edges on the rim itself.
This operation is performed by means of a suitable bead breaking unit, normally present on the tyre changing machine itself.
Bead breaking units of known type comprise an arm with a first extremity hinged to the bed of the tyre changing machine according to a substantially vertical axis and a second extremity having a bead breaking tool, otherwise known as blade.
On the bed is fastened a supporting element, usable to correctly fit the rim during the bead breaking operation.
This supporting element has a supporting surface, otherwise known as pad, which is made of suitable material, and usually knurled in such a way as to increase the friction coefficient with the wheel.
The bead breaking units of known type generally comprise a linear actuator of the type, e.g., of a fluid actuator cylinder for moving the arm.
The liner of the actuator cylinder is hinged to the bed and can be rotated around a vertical axis, while the stem is moving between an extracted position and a retracted position and is associated sliding with the arm.
The stem has a driving element which, during movement from the extracted position to the retracted position, is suitable for engaging on the arm to drive it to the bed.
During use, in an idle position of the bead breaking unit, the stem of the cylinder is normally extracted and the arm, which can be freely rotated around its hinging axis, is in a closer position with respect to the bed of the tyre changing machine due to the action of one return spring.
An operator, once the portion of the wheel to undergo bead breaking has been suitably positioned in correspondence to the pad, manually moves the arm until the blade is positioned in contact with a section of the tyre bead.
Subsequently, the operator starts the actuator cylinder, moving the stem from the extracted position to the retracted position.
This way, the arm is driven by the stem and the blade pushes the tyre bead, detaching it from the edge of the rim.
Subsequently, the stem of the actuator cylinder is moved to extracted position and the operator manually extracts the blade inserted between tyre and rim.
Once the wheel has been removed, the arm is again moved to near position with respect to the bed of the tyre changing machine due to the action of the return spring.
The known bead breaking units do however have a number of drawbacks.
In particular, after bead breaking, the extraction operation of the blade inserted between the tyre and the rim must be performed manually by the operator.
This requires a far from negligible physical effort by the operator, particularly for large wheels, an effort which must often be repeated several times during the course of a day.
Furthermore, in the frequent case of the blade remaining trapped between the tyre bead and the edge of the rim, the job becomes necessary of more than one operator, with the consequent and onerous use of time and personnel.
The document no. EP20100194050 describes a bead breaking unit able to overcome such drawbacks which is able to automatically remove the blade inserted between the tyre and the rim after bead breaking
In this bead breaking unit, in particular, the stem of the actuator has a thrust element which is suitable for engaging on a respective reference element on the arm during the movement of the stem itself from the retracted position to the extracted position so as to move the blade away from the wheel.
Also this known bead breaking unit, nevertheless, is susceptible to upgrading, aimed in particular at permitting greater operating versatility depending on the type of tyre to undergo bead breaking, the size of the tyre itself and/or the particular requirements of the operator using the unit.